The method uses at least one power switch having "on" and "off" states for providing, respectively, low and high impedance paths between an inductive load and a source of power and thereby controls current flow through the inductive load during a sequence of regular reoccurring time periods. The at least one power switch is switched, if in the "off" state, to the "on" state substantially at the beginning of at least some of the time periods. The method is operative during any one of a plurality of the "on" duty periods and switches the at least one power switch from the "on" state to the "off" state when a predetermined level of current flow has been reached in one of the inductive load and the at least on power switch, and switches the at least one power switch back to the "on" state independent of the occurrence of the beginning of a time period.

Pulse width modulated control method and means

An arrangement for driving actuator coils for two or more driven devices employs a microprocessor or similar controller and an actuator driver circuit The actuator driver circuit controls two or more relay actuator coils from a single microprocessor output terminal This output terminal can provide a high, low, or pulse output signal An amplifier switching device, such as a transistor, whose base is coupled to the output terminal of the microprocessor, drives the first relay actuator coil as its load A rectifying diode is connected to one end of a capacitor and thence through a negative resistance device to a second relay actuator coil or other driven device The coil impedances are selected so that the second coil has a significantly higher impedance than the first coil When output pulses appear at the microprocessor output terminal, the transistor switch pulses on and off, and thus energizes the first coil Flyback voltage pulses pass through the rectifier diode to charge up the capacitor until its voltage exceeds the threshold voltage of the negative resistance device Then current flows to energize the second relay actuator coil By selecting the appropriate pulse rate, the microprocessor can energize either or both actuator coils

Energy preservation and transfer mechanism

An electromagnetic actuator having an integral capacitor and secondary coil for reducing opening and closing response times without the need for switching circuits. The secondary coil produces a magnetic field during energization which aids the primary coil in opening the actuator. A capacitor progressively reduces the current flow through the secondary coil as it charges up. During deenergization, the capacitor discharges through the secondary coil, producing a magnetic field which opposes the primary coil's residual magnetic field and aids the closing of the actuator.

Rapid response dual coil electromagnetic actuator with capacitor

An integrated circuit voltage chop circuit for regulating the current in an inductive load is of the type having a fixed off time. A current-sensing comparator produces a reset signal when the current through the driver exceeds a predetermined peak amplitude. A load driver transistor is turned on and off according to the state of a bistable memory elememt, e.g. a flip flop. An external capacitor and external series resistor are connected to the integrated circuit and they determine the driver off time. A voltage comparator having hysteresis produces a high output logic level when the capacitor charges to a predetermined voltage which sets the flip flop and begins to slowly discharge the capacitor. When the capacitor discharges to a lower predetermined voltage, the voltage comparator output goes to a low logic level turning on a shorting transistor that quickly discharges the capacitor completely. A logic gate with an output connected to the reset terminal of the flip flop resets the flip flop when both the output of the voltage comparator is in the low level and the output of the current-sensing comparator produces the reset signal. Thus during the period in which the capacitor is slowly discharging large transient current pulses due to charge storage in the load, i.e., in the recirculation diode and stray capacitance, are blocked from resetting the flip flop. The integrated circuit user may therefore adjust the blocking time by adjusting the external capacitor and then adjust the drive off time by adjusting the external resistor.

Current regulation circuit for inductive loads

Disclosed is an apparatus for controlling the rotational speed of an electric motor based upon the load encountered by the electric motor. A load sensor provides a voltage level based upon the operating load of the electric motor and accumulates this voltage in accordance with the cycle of the alternating current supplied to the motor. If during a cycle of the alternating current, the voltage exceeds a predetermined level, a transistor will be biassed into conduction, said transistor turning off a thyristor and preventing any further conduction of the thyristor during that cycle of the alternating current. Thus the duty cycle of the thyristor determines the total amount of current supplied to the electric motor and this current level determines the rotational rpm of the motor.

Speed control circuit for electric motor

The present invention relates to an electrical circuit for current regulation in DC motors including a sensitivity control means therefor. The circuit includes a means for sensing a predetermined current level in the load of a DC motor. In combination therewith is a subcircuit for cutting-off the load current when the predetermined current level has been reached. Additionally, there is provided means for restoring the load current when, after load current cutoff, the inductive motor current has fallen to a level sufficient to restart the subcircuit.

Joseph W. Fleming

Papers

Current regulator for DC motors including sensitivity control means therefor